This invention relates to conversion systems of the type used to convert circular metal workpieces called shells into can ends, especially easy-open ends. A conversion system is basically a large press having cooperatively-engageable, reciprocable upper and lower tooling. The tooling has appropriate punches and dies which define a plurality of stations wherein shells are progressively converted into can ends. At least one endless conveyor indexes the shells into and through the stations of the tooling. Conversion systems typically have multiple rows or lanes of stations so that multiple ends are formed on each stroke of the press. U.S. Pat. No. 5,017,072, the disclosure of which is incorporated herein by reference, shows further details of the overall conversion system.
The conveyor belt is an endless loop, usually made of steel, and having openings in which the shells rest. The conveyor revolves around head and tail pulleys. Usually the head pulley is driven and the tail pulley is an idler. The tail pulley is mounted on a slide assembly to permit adjustment of the conveyor belt tension. Accurate indexing of the shells requires proper tension on the belt.
Recent advances in tooling permit ends of differing diameters to be made at the same time. That is, one lane can be making one size end while an adjacent lane is making a different size end. Co-pending application Ser. No. 08/001,256, filed Jan. 6, 1993, entitled "End Tooling for Multiple End Diameters", assigned to the present assignee and which is incorporated herein by reference, discloses tooling of this type. Each lane in the multiple-diameter type tooling requires its own conveyor belt, with the openings therein sized for the particular end being made. But the tension of multiple belts cannot be individually adjusted with the slide assemblies of the prior art. Neither can conventional pulleys allow sensing of belt breakage, should it occur. Moreover, conventional pulleys will not adjust for the individual camber of multiple belts. These problems are addressed by the present invention.